File:Quantification-of-Cell-Edge-Velocities-and-Traction-Forces-Reveals-Distinct-Motility-Modules-during-pone.0003735.s005.ogv

English: Velocity Map Analysis (Re: Figure 1). Our algorithms calculate the contour position and the velocity in the direction of the normal to the contour during spreading. The TIRF sequence of an isotropic spreading cell with the contour position overlaid illustrates our technique (left). Each point on the contour is colored to represent the velocity in the direction of the normal to the cell edge at that point (see Fig. 2 for color scale). By stretching out and placing each contour in sequence, we generate the basic unit of our quantitative analysis of cell motility, the velocity map (right). The vertical bars indicate the progression of time. In order to easily compare the TIRF sequence to the velocity maps, keep in mind that the cut in the velocity surface occurs at the point corresponding to the right-most point of the cell in the corresponding TIRF image, and moving in the positive arc-length direction on the velocity-map corresponds to moving clock-wise around the cell edge in the micrograph.